Disposable type thermometer

ABSTRACT

A thermometer having a thermally sensitive substance deposited on a thermally conductive sheet, and an overlying transparent film carrying indicator means which are superpositionably registrable with the thermally responsive substance for communicating therewith to denote specified temperatures upon change of state of the substance is provided with a readily removable flexible shield interposed between the thermally responsive substance and indicator means to prevent communication and reaction between the two until the thermometer is actually required for use. The shield is readily removably adhesively secured to the transparent film and can be peelably removed therefrom by pulling action applied digitally to a pull tab at one end of the shield. Concurrent with peeling of the shield from the transparent film, the latter is pressed against the thermally conductive sheet to position the indicator means in proper overlying communicating registration with the temperature responsive substance on the carrier sheet.

United States Patent Lang 521 mu. ..73/356, 73/358 511 mu....G0lkll/08,G0lkll/l6 [58] Field of Search ..73/358, 356; 1 16/1 14.5;99/192 'lT [56] References Cited UNITED STATES PATENTS 3,175,401 3/1965Geldmacher ..73/ 358 3,430,491 3/ 1969 Gignilliat ....73/358 3,597,9768/l97l Fryar ..73/358 Primary Examiner-Louis R. Prince AssistantExaminer-Denis E. Corr Attorney-Watson Leavenworth & Kelton [451 July18,1972

[57] ABSTRACT A thermometer having a thermally sensitive substancedeposited on a thermally conductive sheet, and an overlying transparentfilm carrying indicator means which are superpositionably registrablewith the thennally responsive substance for communicating therewith todenote specified temperatures upon change of state of the substance isprovided with a readily removable flexible shield interposed between thethermally responsive substance and indicator means to preventcommunication and reaction between the two until the thermometer isactually required for use. The shield is readily removably adhesivelysecured to the transparent film and can be peelably removed therefrom bypulling action applied digitally to a pull tab at one end of the shield.Concurrent with peeling of the shield from the transparent film, thelatter is pressed against the thermally conductive sheet to position theindicator means in proper overlying communicating registration with thetemperature responsive substance on the carrier sheet.

13Claims,6lkawingiigures PATENTED JUL] 8 m2 SHEET 2 0F 2 DISPOSABLE TYPETHERMOMETER BACKGROUND OF THE INVENTION Temperature indicating devices,i.e., thermometers utilizing a thermally responsive substance whichresponsive to temperature change in a test subject, undergoes a changeof state which state change is manifested in suitable indicator means toindicate a precise temperature, are known. One form of such thermometeris disclosed in pending application Ser. No. 058,001 entitledTemperature Indicator filed July 24, I970.

The thermometer described in the aforementioned patent application iscomprised of a thermally conductive sheet in which is formed a number ofcavities, each being filled with a thermally responsive substanceprovided in such quantity and/or composition as permits for change ofthe substance from solid to liquid state in graduated sequenceresponsive to the temperature of the subject being tested. Also providedin that thermometer is an indicator means in suitable form, such as adyestuff, which upon melting of the thermally responsive substance inthe respective cavities cooperates with an acceptor as by migrationthereto, to indicate visually by change of color of the acceptor aprecise condition of temperature associated with each cavity. Overlyingthe conductive sheet is a transparent covering film of a suitablepolymeric material which functions to seal and thereby physicallyisolate the thermally responsive substance, dyestuff and acceptorassociated with each of the respective cavities from communication withany of the others, and also to prevent incursion of foreign matter tothe cavities as well as to prevent direct contact of the subject beingtested with the thermally responsive substance and indicator means. Suchthermometer is well adapted for the intended purpose of measuring thetemperature of the test subject, is reliable in operation and ispossessed of a structural character optimally suited for manufacturingthe thermometer on mass production high speed machinery so that it canbe relatively inexpensively produced and thus be disposable after asingle use. However, the construction of the thermometer described inthe aforementioned application is not such that it possesses a practicalor convenient arrangement of an optimally removable barrier with whichcommunication between the thermally responsive substance and theindicator means can be prevented before the time of actual use of thethermometer on the test subject.

Such barrier ideally should be provided by means which readily andeasily can be incorporated in the thermometer during manufacture on highspeed machinery and should be removable easily and readily from thethermometer at time of use. Further, such means should allow that uponremoval of the communication barrier, the thermometer indicator meansretains proper registration disposition with the thermally responsivesubstance to insure accurate indication of a precise temperature.Removal of the barrier also should be achieved in such a manner as toinsure the sealing of the transparent film to the thermally conductivesheet to prevent the thermally responsive substance from coming intodirect contact with the test subject and to prevent the substance in onecavity from communicating with that in another or the indicator meansassociated with such cavity.

SUMMARY OF THE INVENTION The present invention is concerned generallywith improvements in temperature indicating devices. It is morespecifically concerned with improvements in thermometers which functionon the principle of a temperature induced change in the state of athermally responsive substance to indicate a specified condition oftemperature. A type of thermometer to which it is particularlyapplicable is that described in the aforementioned pending applicationSer. No. 058,001. The thermometer type described in said application canbe comprised of a thermally conductive sheet provided, e.g., as a sheetof metallic foil, and having a film of polymeric material covering oneface surface thereof so as to provide strength and resiliency to thesheet, if required, and also to isolate the foil from direct contactwith the test subject. The thermally conductive sheet can be providedwith a plurality of cavities, and disposed in such cavities on theuncoated face of the foil carrier sheet are a corresponding plurality ofdeposits of thermally responsive substances. The substances filling thecavities are designed with respect to each of the deposits thereof toundergo a change of state at a predetermined temperature and inconjunction with appropriate indicator means to give visual indicationof the temperature of a test subject, the arrangement being such thatthe change of state of the substance in any one cavity is, incooperation with the associated indicator means, indicative of atemperature different from that associated with any other cavity andsubstance deposited therein. The indicator means which overlies thedeposit in each cavity is in the form, e.g., of a pigment or dyestuffand an acceptor such as a filter paper, the arrangement being such thatupon change of state of the thermally responsive substance from solid toliquid state, the dyestuff or pigment causes the acceptor to changecolor and to thereby signal the condition of temperature which initiatedmelting of the temperature responsive substance. Overlying the thermallyconductive sheet, the temperature responsive means and the indicatormeans components is a film of polymeric transparent material whichassists in isolating the elements of the system from the test subjectand in providing structural integrity and resiliency to the thermometerstructure.

In accordance with the present invention there is provided for adisposable type thermometer a separator shield which during themanufacture of the thermometer is removably inserted between thethermally responsive substance and the indicator means to barcommunication therebetween until the thermometer actually is to be used.The shield in one advantageous form thereof, is provided as a strip offlexible material such as aluminum, which may be covered on one or bothof its opposite side faces with a material which is nonreactive with thematerials of the thermometer which it contacts, i.e., the thermallyresponsive substance and the indicator means. The flexible sheetcomprising the shield is folded back upon itself to form at least twoportions thereof which are positioned with the first portion overlyingand coextensive with an indicator section of the carrier sheet, i.e.,the section thereof on which is deposited the thermally responsivesubstance, in covering position over such substance. The second portionof the flexible strip is positioned coextensive with and removablyadhered to the indicator section of the transparent film, i.e., thesection thereof adhesively carrying the indicator means. Removal means,e.g., a pull tab is provided on the shield to facilitate its removalfrom the thermometer preliminary to using the latter. The transparentfilm which overlies the thermometer foil thermally conductive sheet isprovided with an adhesive coating thereon, such adhesive functioning,inter alia, as the means with which the indicator means is secured tothe transparent film. Prior to the use of the thermometer, thetransparent film at the temperature indicating end of the thermometer,along with the shield, lies in close superpositioning above thethermally responsive substance carrying end of the carrier sheet withthe indicator means in register above the deposited masses of thermallyresponsive substance. For convenience, the tab part of the shield may bedisposed so as to extend outwardly longitudinally of the tip end of thethermometer and thus provide a gripping surface on the shield. Byholding the tab and pulling on the other end of the thermometer, or viceversa, the shield is caused to peel away from the underface of thetransparent film to which it is secured in a direction away from thehandle section of such film without affecting the positioning orsecurement of the indicator means to such surface, the pulling forcebeing applied until the shield is completely removed from thethermometer. The transparent film at the temperature indicating end canthen be pressed into registering superpositioned contact with thethermally conductive sheet thereby establishing communication betweenthe temperature responsive substance and the indicator means andrendering the thermometer operative for its intended purpose.

The invention accordingly comprises the thermometer possessing thefeatures, properties and relation of elements which will be exemplifiedin the devices hereinafter described and the scope of the presentinvention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects of the invention will bein part obvious and will in part appear from the following detaileddescription taken in conjunction with the accompanying drawings, whereinlike reference numerals identify like parts throughout and in which:

FIG. 1 is a side elevational view of a thermometer constructed inaccordance with the principles of the present invention and embodying ashield therein which is interposed between the thermally conductivesheet on which is deposited the thermally responsive substance, and thetransparent film on which is received and carried the indicator means,the indicator means and associated indicator section of the trans parentfilm being shown positioned a distance above the indicator section ofthe thermally conductive sheet.

FIG. 2 is a side elevational view of the device shown in FIG. 1 exceptit illustrates the indicator section of the transparent film with theindicator means carried thereon folded down closed against the shieldwhich is sandwiched between the indicator means and the temperatureresponsive substance, the tab on the shield with which shield removal isinitiated being folded inwardly of the adjacent tip end of theindicating end of the thermometer.

FIG. 3 is a perspective view of the thermometer shown in FIGS. 1 and 2with the temperature indicating end opened and the shield in anintermediate position of removal following initiation of the peeling ofthe same from the indicator section of the transparent film but beforecompletion of such removal.

FIG. 4 is a side elevational view of a thermometer showing schematicallythe manner of removing the shield and the manner in which the indicatorsection of the transparent film concurrently is pressed against thethermally responsive substance on the thermally conductive sheet toregistrably superposition the indicator means on the thermallyresponsive substance and seal the indicating end of the thermometer withthe transparent film.

FIG. 5 is a vertical sectional view of the temperature indicating end ofthe thermometer shown in FIGS. 1-4 on greatly enlarged scale with thetransparent film indicator section pressed closed against the shieldwhich in turn is interposed between the former and the thermallyresponsive substance deposited on the thermally conductive sheet.

FIG. 6 is a plan view depicting a thermometer following use thereof forrecording the temperature of a test subject.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention isconcerned with an improved form of thermometer and particularly athermometer of disposable character, i.e., one which can be discardedfollowing a single use. Accordingly, such thermometer must be easy andinexpensive to make. It must be simple to use and provide optimumaccuracy of temperature indication respecting the test subject and beharmless to use when employed for human testing application. Further,the thermometer which embodies a thermally responsive chemical substancein conjunction with an indicator means should be designed to beinoperative until actual use, i.e., the thermally responsive substanceshould be isolated from communicating with the indicator means untilsuch communication is necessary for operative use of the thermometer. Inthis manner temporary and inadvertent change of state of the thermallyresponsive substance will not result in indication oftemperature.

In the ensuing description of the improved thermometer provided by thepresent invention, continuing reference should be had to FIGS. 1-3 ofthe drawings. Referring now to such FIGURES, the thermometer 10 iscomprised of a thermally conductive sheet 12 in which is formed aplurality of depressions or cup-shaped cavities 14, the cavities beingpro vided in such numbers as may be required to provide a reasonablerange of temperature indication depending on the subject for which thethermometer is to be used. Thus, with respect to testing humans, atemperature range capacity of between 96F. and 104.8F. is acceptablewith each degree being further graduated in two-tenths of a degree,there being provided a separate cavity 14 for each of the last-mentionedgraduations, the pattern of the cavity disposition and associatedtesting range being evident by reference to FIG. 6 from which it may benoted a printing of indicia also can be provided on the carrier sheet todenote specific temperature values. Sheet 12 conveniently is provided asa sheet or strip of a good thermally conductive material such as a foilof a metal, e.g., an aluminum foil which has a certain strength andwhich is a good thermally conductive material for enhancing transmissionof heat to the thermally responsive substance 16 deposited in eachcavity 14 (FIG. 5). The thermally responsive substance 16 can be achemical system suited for the intended purpose, e.g., one of thecompositions described in the concurrently filed application of ZsigmondSagi et al antitled A Temperature Indicator". As can be noted best fromFIG. 3, the thermally conductive sheet 12 has a first longitudinalportion shown generally at 22 which defines or provides an indicatorsection for such sheet, and a remaining longitudinal portion showngenerally at 24 which provides a handle section.

To increase the overall strength of the thermally conductive sheet 12and to prevent accidental puncture of the cavities 14 as when thethermometer is received in a human test subjects mouth and therebypreclude mouth contact with the thermally responsive substance 16, thethermally conductive sheet 12 can be provided at the face thereofopposite that on which the thermally responsive substance is deposited,with a layer 18 or coating of a polymeric material such as Mylar, thelayer 18 being coextensive with the sheet 12 and affixed thereto in anysuitable manner, the layer conformally contouring as at 20 with thecup-shaped cavities 14.

Overlying the thermally conductive sheet 12 and of coextensive charactertherewith is a transparent film 26 of polymeric material which likelayer 18 preferably is Mylar and which serves, as will appear later, anumber of important purposes including providing a support for indicatormeans shown generally at 28. Transparent film 26 also has portionsthereof defining an indicator section 122 and a handle section 124corresponding with indicator section 22 and handle section 24respectively of the thermally conductive sheet 12. The underface oftransparent film 26 is provided with an adhesive coating, such adhesivebeing generally a pressure sensitive type as which will permit peelableremoval therefrom of a shield adhesively secured thereto in a manner tobe described later. Such adhesive, as will be apparent from furtherdescription herein, should be inert respecting the thermally responsivesubstance 14 so as to not affect its operative functioning. An adhesivesuitable for use with Mylar is one incorporated in a product sold byJohnson and Johnson of New Brunswick, N.J., under the trademark J-Lar.The handle section 124 of the transparent film 26 is adhesively securedin face-to-face contact with the corresponding section 24 of thethermally conductive sheet 12 and remains in that arrangementpermanently following manufacture of the thermometer. The otherindicator section 122 of the transparent film 26,as mentioned earlier,provides a support for carrying the indicator means 28 which means canbe provided as a plurality of indicator components, e.g., a matrix ofpaper dots adhered to the surface of transparent film 26 in number andpositioning in correspondence to the arrangement of cavities 14 in thesheet 12. With the transparent film 26 pressed down in the positionshown in FIG. 2 or in the manner depicted in FIG. 5, each of theindicator means 28 lies disposed superpositioned registrably with one ofthe cavities 14.

The present invention provides that the thermometer 10 remainsinoperative to detect and indicate a temperature value until actuallyrequired for use on a test subject at which time it can be renderedoperative in a matter of a few seconds, all of the foregoing beingachieved without sacrifice to the reliability or accuracy of thethermometer. For this purpose, thermometer is provided with a shield 30interposed between the thermally responsive substance 16 and theindicator means 28 to prevent communication therebetween until such timeas the thermometer is to be used. A more particular description of theshield 30 will be given next.

Shield 30 conveniently is formed from a flexible material such as a foilof aluminum, the basic shield form being provided as an elongated foilstrip covered on one or both of its opposite faces with coatings ofsuitable polymeric material and embodying pull tab means for initiatingremoval of the shield. As seen in FIG. 1, the shield 30 is formed suchthat it is folded upon itself in at least one fold along a fold line 32to provide a first shield portion 34 generally coextensive with theindicator section 22 of the thermally conductive sheet 12 and normallydisposed in overlying but unsecured contact with indicator section 22,and a second shield portion 36 coextensive with the indicator section122 of the transparent film 26. The shield 30 also is provided with asecond fold therein along a second fold line 38 to provide a thirdshield portion 40 which serves as a pull tab for digitally initiatingremoval of the shield from its operative position in the thermometer.The second portion 36 of the shield is coextensive with and adhesivelysecured to the underface of the indicator section 122 of the transparentfilm 26 and accordingly covers the respective indicator means 28adhesively secured to such transparent film in the manner earlierdescribed. The adhesive bond between the shield second portion 36 andtransparent film is not such as removal of the shield from thethermometer induces or promotes any stretching of transparent film 26which could prevent achieving proper registration of the indicator means28 with the thermally responsive substance when pressing indicatorsection 122 into sealing contact with indicator section 22. At the sametime such bond is sufficient to hold the shield second portion 36 infirm face-to-face contact with the transparent film 26 to prevent anyvolatilization of solvent from the adhesive on the film or the admissionto the indicator means of any vapor of sublimation of the thermallyresponsive substance deposited in the discrete cavities 14 if suchshould occur while the thermometer is stored during a non-use periodwhen the indicator section 122 of the transparent film normally liespressed down in close contact over the indicator section 22 of thethermally conductive sheet 12 with the shield 30 sandwiched therebetweenas depicted in FIG. 2.

The thermometer 10 prior to use normally is not operative to record atemperature value. If it is desired to use the thermometer on a testsubject and thus render it operative, such change can be accomplishedmost expeditiously. In inoperative condition, as depicted in FIG. 2,shield 30 is sandwiched between the indicator section 122 of transparentfilm 26 and indicator section 22 of carrier sheet 12. As a preliminary,the indicator section 122 can be opened, i.e., swung upwardly, to theposition shown in FIGS. 1 and 3 to provide access to pull tab 40 fordigital grasping of the same, whereupon the pull tab is swung aboutsecond fold line 38 adjacent the tip end of the thermometer andoutwardly of the thermometer indicating end beyond the tip end thereof.In removing the shield, the use may initiate peeling by applying apulling force to the pull tab 40 while holding the thermometer near thejuncture of the respective indicator sections and handle sections of thethermally conductive sheet 12 and transparent film 26, or by holding thepull tab 40 and applying the pulling force to the thermometer to peelthe shield in a direction away from the handle section of thetransparent film. For the purpose of providing reinforcement of the pulltab portion of the shield to prevent accidental severance of the formerfrom the latter, a reinforcing tape strip 41 can be applied to one faceof the pull tab to obviate such possibility of tearing of the same atthe initial action of peeling. The application of such pulling force ofmoderate magnitude is effective to initiate peeling of the secondportion 36 away from the underface of transparent film indicator section122 starting at fold line 32 which as can be seen in FIGS. 1 and 2, isdisposed adjacent the juncture of the respective indicator sections andhandle sections. Continued application of the pulling force will resultin the peeling away of the shield second portion 36 in the manner shownin FIGS. 3 and 4 in a direction away from the transparent film handlesection 124 until the second portion 36 is completely removed from itsadhesive contact with the underface of transparent film indicatorsection 122 and without disturbing the positioning of the indicatormeans 28 secured to the transparent film 26. During peeling removal ofshield 30 from the thermometer if same is accomplished wholly by digitalmanipulation, the transparent film indicator section 122 carryingindicator means 28 will not become displaced, i.e., swung upwardly, toofar from the indicator section 22 of sheet 12 so that following completeremoval of the shield, the user need employ only a light pressing forceagainst the transparent film indicator section 122 to put it inface-to-face contact with the carrier sheet indicator section 22 andbring the indicator means 28 into superposed registration with thethermally responsive substance filled cavities 14 placing suchcomponents in communication and thereby rendering the thermometeroperative for its intended use. The removal of shield 30 from thethermometer l0 and pressing or sealing of transparent film indicatorsection 122 against the thermally conductive sheet indicator section 22also can be accomplished by means of devices within a dispenser of thetype described in the concurrently filed application of Charles G.Pickett et al. entitled Dispenser for Disposable Type Thermometers. In adispenser of the type described in said Pickett et al. application, thethermometer 10 can bereceived therein with the pull tab 40 thereofstaked over a post means 220 (FIG. 4) for which purpose the pull tabsare provided with staking holes 31. Thus, when a pulling force X isapplied to the opposite or handle end of the thermometer, the shieldwill remain anchored in the dispenser while the thermometer exitstherefrom, the shield peeling off as depicted in FIG. 4. Concurrently, ablade spring 240 in the dispenser applies pressing force to thetransparent film indicator section 122 to seal it against the thermallyconductive sheet.

With the thermometer now in operative condition, it can be used on atest subject. For example, it can be received in a persons mouth inconventional manner whereupon the thermally conductive sheet immediatelyconducts heat from the person s mouth to the thermally responsivesubstance in the various cavities 14. Since such substance is amenableto change of state, e.g., from a solid state to a liquid state atpredetermined temperature, the substance in selected cavities will,depending upon the temperature of the test subject, change state and theindicator means associated with such selected cavities operativelyrespond to change of state to evidence initiation of such state changeand signal the temperature of the test subject. FIG. 6 illustrates suchtemperature recordation which in the depicted example is 98.6F. Asmentioned earlier in this description, the indicator means 28 may beprovided in various ways. In the depicted embodiment, the indicatormeans includes a dyestuff 42 and an acceptor 44 of an absorbentmaterial. The dyestuff 42, e.g., a printed coating on the surface ofacceptor 44 becomes wetted upon melting of the thermally responsivesubstance and migrates therewith to the acceptor 44, the appearance ofthe dyestuff through transparent film 28 being the visual evidence ofthe recorded temperature value. Other suitable arrangements of indicatormeans also could be employed.

With reference to FIG. 5 further features embodied in the shield 30 maybe readily noted. FIG. 5 shows on greatly enlarged scale the conditionof the indicator end of a thermometer 10 stored ready for use, e.g., ina suitable dispenser and in which condition it (the thermometer) is acompact structure with the respective components at the indicator endpressed down in relatively tight abutment with each other. It isdesirable that the shield be provided on one or both of its oppositeThus for this purpose the flexible strip comprising shield 30 can becoated with a synthetic material such as nitrocellulose on the facethereof which is disposed against both the thermally responsivesubstance 16 and the indicator means 28. The other face of the shield,if desired, can be coated as at 262 with a layer of polyethylene. Themanner of thus coating the shield provides the advantageous resultsstated above and additionally facilitates readily peeling the shieldaway from the indicator section 122 of transparent film 26 withoutdisrupting the positioning of the indicator means. A further advantageof coating the shield with the material layer 260 is that such materiallayer overlays the entrance opening of the cavities 14 carrying thesubstance 16 and acts to seal such opening to prevent sublimation of thesubstance 16 while the thermometer is stored.

It will be apparent from a reading of the foregoing that the thermometerof the present invention while described in a representative embodimentas being used for human test subjects, can be used for other purposes ina wide range of commercial and industrial applications, particularlywhere it is desired to maintain the indicator means out of communicationwith the thermally responsive substance until needed for use to therebypreclude inoperability of the thermometer devices by accidental exposureto elevated temperatures.

WHAT IS CLAIMED IS:

1. A thermometer comprising an elongated thermally conductive sheethaving a first longitudinal portion providing an indicator section, theremaining longitudinal portion of said sheet providing a handle section,

a thermally responsive substance deposited on said thermally conductivesheet within the indicator section thereof, said substance beingamenable to change of state at a predetermined temperature,

a shield in overlying but unsecured contact with the indicator sectionof said thermally conductive sheet, and covering said thermallyresponsive substance,

a transparent film coextensive with said thermally conductive sheet andhaving longitudinal portions thereof corresponding with the indicatorsection and handle section of said thermally conductive sheet, saidtransparent film having an adhesive face, the handle section of saidtransparent film being adhesively secured to the handle section of saidthermally conductive sheet, and

indicator means on the indicator section adhesive face of saidtransparent film, said indicator means when in communication with saidthermally responsive substance being operably responsive to a change instate of said substance to evidence initiation of such state change,said shield covering said indicator means and being removably adhesivelysecured to the indicator section of said transparent film,

said shield embodying pull tab means for peelably removing said shieldfrom the indicator section of said transparent film in a direction awayfrom the handle section of said transparent film, said indicator meansbeing positioned on said transparent film indicator section such as tooverlyingly registerably communicate with said thermally responsivesubstance when said shield is removed and the indicator section of saidtransparent film is pressed against the indicator section of saidcarrier sheet.

2. The thermometer of claim 1 wherein said thermally conductive sheet isprovided with a plurality of shaped cavities in the indicator sectionthereof, said thermally responsive substance being deposited in each ofsaid cavities, the respective cavities and thermally responsivesubstance therein being each associated with a predetermined temperaturevalue different than that associated with any other cavity.

3. The thermometer of claim 1 wherein said shield is comprised of astrip of flexible material folded upon itself in at least one fold alonga fold line to rovide a first shield portion at least coextensive withthe in water section of said thermally conductive sheet and a secondshield portion coextensive with the indicator section of saidtransparent film, said tab means being embodied in said first shieldportion.

4. The thermometer of claim 3 wherein the shield is disposed such thatsaid fold line is proximate the juncture of the respective indicatorsections and handle sections of said thermally conductive sheet and saidtransparent film.

5. The thermometer of claim 4 wherein said shield is provided with asecond fold of said strip of flexible material upon itself along asecond fold line to provide a third shield portion joined with saidfirst shield portion, said second fold line being remote from thefirst-mentioned fold line and adjacent the tip end of said thermallyconductive sheet indicator section, said third shield portion beingreadily foldable in one direction to a position wherein it liessandwiched intermediate said first and second portions and in anopposite direction outwardly of the tip end of said thermally conductivesheet indicator section, said third shield portion providing said pulltab means for digitally initiating peeling of said second shield portionfrom the indicator section of said transparent film.

6. The thermometer of claim 5 wherein said third shield portion isprovided with reinforcing means to prevent severance of said thirdshield portion from said first shield portion when pulling force isapplied thereto.

7. The thermometer of claim 6 wherein said reinforcing means comprise astrip of reinforcing tape adhered to said third shield portion.

8. The thermometer of claim 1 wherein said shield comprises a strip of afoil of a metal.

9. The thermometer of claim 8 wherein said strip of foil is coated witha material impermeable to both said thermally responsive substance andthe adhesive on said transparent film.

10. The thermometer of claim 1 wherein said indicator means comprises adyestuff and an absorbent material which absorbs the dyestuff and atleast some of said thermally responsive substance when the latterundergoes a change of state to evidence initiation of such change. 1

11. The thermometer of claim 10 wherein said thermally responsivesubstance is a normally solid solution which melts at said predeterminedtemperature, said dyestuff comprising a printed coating thereof on asurface part of said absorbent material, said dyestuff being solubilizedby said substance upon initiation of melting of the same.

12. The thennometer of claim 1 wherein said thermally conductive sheetis a foil of a metal having opposite face surfaces, the thermallyresponsive substance being deposited on one of said face surfaces.

13. The thermometer of claim 12 wherein the other face surface of saidthermally conductive sheet is provided with a coating of a polymericmaterial.

1. A thermometer comprising an elongated thermally conductive sheethaving a first longitudinal portion providing an indicator section, theremaining longitudinal portion of said sheet providing a handle section,a thermally responsive substance deposited on said thermally conductivesheet within the indicator section thereof, said substance beingamenable to change of state at a predetermined temperature, a shield inoverlying but unsecured contact with the indicator section of saidthermally conductive sheet, and covering said thermally responsivesubstance, a transparent film coextensive with said thermally conductivesheet and having longitudinal portions thereof corresponding with theindicator section and handle section of said thermally conductive sheet,said transparent film having an adhesive face, the handle section ofsaid transparent film being adhesively secured to the handle section ofsaid thermally conductive sheet, and indicator means on the indicatorsection adhesive face of said transparent film, said indicator meanswhen in communication with said thermally responsive substance beingoperably responsive to a change in state of said substance to evidenceinitiation of such state change, said shield covering said indicatormeans and being removably adhesively secured to the indicator section ofsaid transparent film, said shield embodying pull tab means for peelablyremoving said shield from the indicator section of said transparent filmin a direction away from the handle section of said transparent film,said indicator means being positioned on said transparent film indicatorsection such as to overlyingly registerably communicate with saidthermally responsive substance when said shield is removed and theindicator section of said transparent film is pressed against theindicator section of said carrier sheet.
 2. The thermometer of claim 1wherein said thermally conductive sheet is provided with a plurality ofshaped cavities in the indicator section thereof, said thermallyresponsive substance being deposited in each of said cavities, therespective cavities and thermally responsive substance therein beingeach associated with a predetermined temperature value different thanthat associated with any other cavity.
 3. The thermometer of claim 1wherein said shield is comprised of a strip of flexible material foldedupon itself in at least one fold along a fold line to provide a firstshield portion at least coextensive with the indicator section of saidthermally conductive sheet and a second shield portion coextensive withthe indicator section of said transparent film, said tab means beingembodied in said first shield portion.
 4. The thermometer of claim 3wherein the shield is disposed such that said fold line is proximate thejuncture of the respective indicator sections and handle sections ofsaid thermally conductive sheet and said transparent film.
 5. Thethermometer of claim 4 wherein said shield is provided with a secondfold of said strip of flexible material upon itself along a second foldline to provide a third shield portion joined with said first shieldportion, said second fold line being remote from the first-mentionedfold line and adjacent the tip end of said thermally conductive sheetindicator section, said third shield portion being readily foldable inone direction to a position wherein it lies sandwiched intermediate saidfirst and second portions and in an opposite direction outwardly of thetip end of said thermally conductive sheet indicator section, said thirdshield portion providing said pull tab means for digitally initiatingpeeling of said second shield portion from the indicator section of saidtransparent film.
 6. The thermometer of claim 5 wherein said thirdshield portion is provided with reinforcing means to prevent severanceof said third shield portion from said first shield portion when pullingforce is applied thereto.
 7. The thermometer of claim 6 wherein saidreinforcing means comprise a strip of reinforcing tape adhered to saidthird shield portion.
 8. The thermometer of claim 1 wherein said shieldcomprises a strip of a foil of a metal.
 9. The thermometer of claim 8wherein said strip of foil is coated with a material impermeable to bothsaid thermally responsive substance and the adhesive on said transparentfilm.
 10. The thermometer of claim 1 wherein said indicator meanscomprises a dyestuff and an absorbent material which absorbs thedyestuff and at least some of said thermally responsive substance whenthe latter undergoes a change of state to evidence initiation of suchchange.
 11. The thermometer of claim 10 wherein said thermallyresponsive substance is a normally solid solution which melts at saidpredetermined temperature, said dyestuff comprising a printed coatingthereof on a surface part of said absorbent material, said dyestuffbeing solubilized by said substance upon initiation of melting of thesame.
 12. The thermometer of claim 1 wherein said thermally conductivesheet is a foil of a metal having opposite face surfaces, the thermallyresponsive substance being deposited on one of said face surfaces. 13.The thermometer of claim 12 wherein the other face surface of saidthermally conductive sheet is provided with a coating of a polymericmaterial.